Using Queue class in C#

Using Queue class in C#

by: amsprasad

Summary

The Source code of the Queue Class usage in C#. WinForms App which visually shows the Queue. Below is the Doc to show the usage of Queue Class. Just compile the QueueDemo.cs file using csc QueueDemo.cs and run QueueDemo.exe to see the sample.

Queue is a Simple DataStucture which allows Insert/Remove of Items at one of the ends only. It is basically called as FIFO(First In First Out) data structure. ie The item which is added first is the first one to be removed. .NET has a built in class for Queue. It is foundin System.Collections namespace.

1. How to Create a Queue?

Queue q = new Queue(32);

32 is the intial size of the Queue. It is always better to give intially size so that the Insert/Remove operations are performed efficiently with out re-arranging the elements.

2. How to add an element to the Queue?

  q.Enqueue(12);

Enqueue() will add an element to the Queue. The item is inserted at the last available position of the queue.

3. How to Remove an Element?

  object ob = q.Dequeue()

Dequeue() will return the element which is added very old and also removes the item from the Queue. It throws Exception when the Queue is Empty.

4. What if i need to just see the Top element without removing it from the Queue?

Queue class has a method called Peek() which return the top element of the Queue. It is very similar to Dequeue() except that it would not remove the element from the Queue.

Prasad

The Code:

using System;
using System.Collections;
using System.Windows.Forms;
using System.Drawing;

class QueueDemo : Form
{
    static Queue simpleQueue;
    Button btnEnQueue,btnPeek,btnDeQueue;
    TextBox txtItem;
    Label lblItem,lblQueue;
    ListBox lstQueueUI;
    
    public QueueDemo()
    {
        simpleQueue = new Queue(32);
        lblItem = new Label();
        lblItem.Text = "Item To Add";
        lblItem.Location = new Point(16,16);
        lblItem.AutoSize = true;
        
        txtItem = new TextBox();
        txtItem.Location = new Point(lblItem.Right + 8 ,lblItem.Top);
        txtItem.Size = new Size(256,27);
        
        btnEnQueue = new Button();
        btnEnQueue.Size = btnEnQueue.Size;
        btnEnQueue.Location = new Point(txtItem.Right + 8,lblItem.Top);
        btnEnQueue.Text = "EnQueue";
        btnEnQueue.Click += new EventHandler(btnEnQueue_Click);
        
        btnPeek = new Button();
        btnPeek.Size = btnEnQueue.Size;
        btnPeek.Location = new Point(btnEnQueue.Right + 8,lblItem.Top);
        btnPeek.Text = "Peek";
        btnPeek.Click += new EventHandler(btnPeek_Click);
        
        btnDeQueue = new Button();
        btnDeQueue.Size = btnEnQueue.Size;
        btnDeQueue.Location = new Point(btnPeek.Right + 8,lblItem.Top);
        btnDeQueue.Text = "DeQueue";
        btnDeQueue.Click += new EventHandler(btnDeQueue_Click);
        
        lblQueue = new Label();
        lblQueue.Location = new Point(lblItem.Left,lblItem.Bottom + 32);
        lblQueue.Text = "Visual Queue";
        
        lstQueueUI = new ListBox();
        lstQueueUI.Location = new Point(lblItem.Left,lblQueue.Bottom + 16);
        lstQueueUI.Size = new Size(512,256);
        
        this.Text = "Queue Demo";        
        this.Controls.AddRange( new Control[]
            {
                lblItem,txtItem,
                btnEnQueue,btnPeek,btnDeQueue,
                lblQueue,lstQueueUI
            });
    }
    
    void btnEnQueue_Click(object sender,EventArgs e)
    {
        if(txtItem.Text.Trim() != String.Empty)
        {
            simpleQueue.Enqueue(txtItem.Text.Trim());
            lstQueueUI.Items.Insert(lstQueueUI.Items.Count,
"Added Element: " + txtItem.Text.Trim() + " At " + DateTime.Now.ToString());
        }
        else
        {
            MessageBox.Show("Empty Value Cannot be Added","QueueDemo",
MessageBoxButtons.OK,MessageBoxIcon.Information);
        }
    }
    
    void btnPeek_Click(object sender,EventArgs e)
    {
        try
        {
            MessageBox.Show("Peek Element: "  
+ simpleQueue.Peek().ToString());
        }
        catch(Exception ex)
        {
            MessageBox.Show("Error: " + ex.Message,"QueueDemo",
MessageBoxButtons.OK,MessageBoxIcon.Error); 
        }
    }
    
    void btnDeQueue_Click(object sender,EventArgs e)
    {
        try
        {
            MessageBox.Show("Removed Element: "  + 

simpleQueue.Dequeue().ToString());
            lstQueueUI.Items.RemoveAt(0);
        }
        catch(Exception ex)
        {
            MessageBox.Show("Error: " + ex.Message,"QueueDemo",
MessageBoxButtons.OK,MessageBoxIcon.Error); 
        }
    }
    
    static void Main()
    {
        Application.Run(new QueueDemo());
    }
}